By using properties of determinants,show that:
$\left|\begin{array}{ccc} 1 & 1 & 1 \\ a & b & c \\ a^{3} & b^{3} & c^{3} \end{array}\right|=(a-b)(b-c)(c-a)(a+b+c)$

Vedclass pdf generator app on play store
Vedclass iOS app on app store
(A) Let $\Delta=\left|\begin{array}{lll}1 & 1 & 1 \\ a & b & c \\ a^{3} & b^{3} & c^{3}\end{array}\right|$.
Applying $C_{1} \rightarrow C_{1}-C_{2}$ and $C_{2} \rightarrow C_{2}-C_{3}$,we have:
$\Delta=\left|\begin{array}{ccc}0 & 0 & 1 \\ a-b & b-c & c \\ a^{3}-b^{3} & b^{3}-c^{3} & c^{3}\end{array}\right|$.
Taking common factors $(a-b)$ from $C_{1}$ and $(b-c)$ from $C_{2}$:
$\Delta=(a-b)(b-c)\left|\begin{array}{ccc}0 & 0 & 1 \\ 1 & 1 & c \\ a^{2}+ab+b^{2} & b^{2}+bc+c^{2} & c^{3}\end{array}\right|$.
Applying $C_{1} \rightarrow C_{1}-C_{2}$:
$\Delta=(a-b)(b-c)\left|\begin{array}{ccc}0 & 0 & 1 \\ 0 & 1 & c \\ a^{2}-c^{2}+ab-bc & b^{2}+bc+c^{2} & c^{3}\end{array}\right|$.
$\Delta=(a-b)(b-c)\left|\begin{array}{ccc}0 & 0 & 1 \\ 0 & 1 & c \\ (a-c)(a+c)+b(a-c) & b^{2}+bc+c^{2} & c^{3}\end{array}\right|$.
$\Delta=(a-b)(b-c)(a-c)\left|\begin{array}{ccc}0 & 0 & 1 \\ 0 & 1 & c \\ a+b+c & b^{2}+bc+c^{2} & c^{3}\end{array}\right|$.
Expanding along $R_{1}$:
$\Delta=(a-b)(b-c)(a-c)(1)[0 - (a+b+c)] = -(a-b)(b-c)(a-c)(a+b+c)$.
Since $-(a-c) = (c-a)$,we get:
$\Delta=(a-b)(b-c)(c-a)(a+b+c)$.
Hence,the result is proved.

Explore More

Similar Questions

The determinant $\left| \begin{array}{ccc} 1 & 1 & 1 \\ 1 & 2 & 3 \\ 1 & 3 & 6 \end{array} \right|$ is not equal to

$A$ value of $\theta$ lying between $0$ and $\frac{\pi}{2}$ and satisfying $\left|\begin{array}{ccc} 1+\sin^2 \theta & \cos^2 \theta & 4\sin 4\theta \\ \sin^2 \theta & 1+\cos^2 \theta & 4\sin 4\theta \\ \sin^2 \theta & \cos^2 \theta & 1+4\sin 4\theta \end{array}\right| = 0$ is:

Let $A = [a_{ij}]$ and $B = [b_{ij}]$ be two $3 \times 3$ real matrices such that $b_{ij} = (3)^{(i+j-2)} a_{ji}$,where $i, j = 1, 2, 3$. If the determinant of $B$ is $81$,then the determinant of $A$ is:

If $A, B$ and $C$ are $n \times n$ matrices and $\det(A) = 2$,$\det(B) = 3$ and $\det(C) = 5$,then the value of $\det(A^2BC^{-1})$ is equal to

The value of the determinant $\left|\begin{array}{ccc}1+a^{2}-b^{2} & 2 a b & -2 b \\ 2 a b & 1-a^{2}+b^{2} & 2 a \\ 2 b & -2 a & 1-a^{2}-b^{2}\end{array}\right|$ is

Vedclass Products

For Students

Vedclass Test Series

Mock tests in real JEE/NEET style with performance analysis. 5-day free trial.

Start Free Trial
For Teachers

Exam Paper Generator

Generate Set A/B/C/D exam papers from 7.5L+ questions in 2 minutes. 3 chapters free.

Try Free
For Institutes

Online Exam Module

Live online exams with unlimited students, 360° analytics & white-label branding.

See Demo